The need to secure items one to another has existed since before the beginnings of civilized societies. Today, one of the most commonly used fasteners for joining several structural members together is the threaded bolt and nut. These fasteners, being widely used in many applications, are now commonly mass produced in various standard sizes at a relatively low cost.
A bolt has a head and a cylindrical threaded body that extends from the head. The head can be of various shapes, such as hexagonal, square or domed, and the threaded body can be of various lengths. The nut that mates to the bolt is generally hexagonal or square in shape and has a corresponding threaded through hole. Threaded fasteners such as hex-head bolt and nut sets or carriage bolt and nut sets allow the separation of the affixed parts by using commonly available standard wrenches, sockets and similar tools to undo the fasteners. Because of common availability of such tools, the unauthorized tampering with exposed nuts and bolts in public areas is a significant and ongoing problem.
Sheet metal signage is commonly used for advertisement and traffic control. These consist of sheet metal signs mounted on vertical posts or on flat vertical surfaces. These signs have become popular targets for theft and vandalism. Such theft and vandalism create many problems for society. They range from missed directions for motorists, property loss due of replacement to fatal traffic accidents. For example, many municipalities annually spend thousands of dollars each just to replace vandalized traffic control signs. Moreover, there have been instances where the unauthorized removal of stop signs at a busy intersection caused a vehicle collision resulting in the loss of human life.
In order to address the potential of vandalism of signage, some municipalities have resorted to connecting the signs to their support posts by means of non-releasable rivets. While this makes removal of the sign difficult to potential vandals or thieves, it unfortunately makes removal difficult for authorized personnel as well.
An anti theft technology taught by U.S. Pat. No. 4,841,838 permanently attaches a frusto-conical collar circumjacent to a hexagonal bolt head after the bolt is installed, thus rendering the bolt head not accessible to wrenches or similar tools. In order to turn the bolt head, the frusto-conical collar must be cut away with a torch first. This again limits access by authorized personnel.
In an effort to provide security fasteners that are readily removable by authorized personnel but not vandals, several technologies have been invented that require a non-standard bolt or nut which require non-standard tooling to rotate such non-standard bolt or nut thus limiting access to such bolt or nut to personnel in possession of the non-standard tooling. Here the non-standard bolts and/or nuts are expected to cost much more than the mass-produced standard nuts and bolts thus rendering them uneconomical for the application.
Therefore, there is a need to develop fasten systems for sheet metal signs that are not easily accessible to the general public and yet allow authorized personal to remove and/or replace the signs with relative ease. The present invention intends to provide such a system of security fastener utilizing low cost standard bolt and nut sets.